/* Copyright (c) 2006 Brandon Aaron (http://brandonaaron.net)
* Dual licensed under the MIT (http://www.opensource.org/licenses/mit-license.php) 
* and GPL (http://www.opensource.org/licenses/gpl-license.php) licenses.
*
* $LastChangedDate: 2007-07-21 18:44:59 -0500 (Sat, 21 Jul 2007) $
* $Rev: 2446 $
*
* Version 2.1.1
*/

(function ($) {

    /**
    * The bgiframe is chainable and applies the iframe hack to get 
    * around zIndex issues in IE6. It will only apply itself in IE6 
    * and adds a class to the iframe called 'bgiframe'. The iframe
    * is appeneded as the first child of the matched element(s) 
    * with a tabIndex and zIndex of -1.
    * 
    * By default the plugin will take borders, sized with pixel units,
    * into account. If a different unit is used for the border's width,
    * then you will need to use the top and left settings as explained below.
    *
    * NOTICE: This plugin has been reported to cause perfromance problems
    * when used on elements that change properties (like width, height and
    * opacity) a lot in IE6. Most of these problems have been caused by 
    * the expressions used to calculate the elements width, height and 
    * borders. Some have reported it is due to the opacity filter. All 
    * these settings can be changed if needed as explained below.
    *
    * @example $('div').bgiframe();
    * @before <div><p>Paragraph</p></div>
    * @result <div><iframe class="bgiframe".../><p>Paragraph</p></div>
    *
    * @param Map settings Optional settings to configure the iframe.
    * @option String|Number top The iframe must be offset to the top
    * 		by the width of the top border. This should be a negative 
    *      number representing the border-top-width. If a number is 
    * 		is used here, pixels will be assumed. Otherwise, be sure
    *		to specify a unit. An expression could also be used. 
    * 		By default the value is "auto" which will use an expression 
    * 		to get the border-top-width if it is in pixels.
    * @option String|Number left The iframe must be offset to the left
    * 		by the width of the left border. This should be a negative 
    *      number representing the border-left-width. If a number is 
    * 		is used here, pixels will be assumed. Otherwise, be sure
    *		to specify a unit. An expression could also be used. 
    * 		By default the value is "auto" which will use an expression 
    * 		to get the border-left-width if it is in pixels.
    * @option String|Number width This is the width of the iframe. If
    *		a number is used here, pixels will be assume. Otherwise, be sure
    * 		to specify a unit. An experssion could also be used.
    *		By default the value is "auto" which will use an experssion
    * 		to get the offsetWidth.
    * @option String|Number height This is the height of the iframe. If
    *		a number is used here, pixels will be assume. Otherwise, be sure
    * 		to specify a unit. An experssion could also be used.
    *		By default the value is "auto" which will use an experssion
    * 		to get the offsetHeight.
    * @option Boolean opacity This is a boolean representing whether or not
    * 		to use opacity. If set to true, the opacity of 0 is applied. If
    *		set to false, the opacity filter is not applied. Default: true.
    * @option String src This setting is provided so that one could change 
    *		the src of the iframe to whatever they need.
    *		Default: "javascript:false;"
    *
    * @name bgiframe
    * @type jQuery
    * @cat Plugins/bgiframe
    * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
    */
    $.fn.bgIframe = $.fn.bgiframe = function (s) {
        // This is only for IE6
        if ($.browser.msie && /6.0/.test(navigator.userAgent)) {
            s = $.extend({
                top: 'auto', // auto == .currentStyle.borderTopWidth
                left: 'auto', // auto == .currentStyle.borderLeftWidth
                width: 'auto', // auto == offsetWidth
                height: 'auto', // auto == offsetHeight
                opacity: true,
                src: 'javascript:false;'
            }, s || {});
            var prop = function (n) { return n && n.constructor == Number ? n + 'px' : n; },
		    html = '<iframe class="bgiframe"frameborder="0"tabindex="-1"src="' + s.src + '"' +
		               'style="display:block;position:absolute;z-index:-1;' +
			               (s.opacity !== false ? 'filter:Alpha(Opacity=\'0\');' : '') +
					       'top:' + (s.top == 'auto' ? 'expression(((parseInt(this.parentNode.currentStyle.borderTopWidth)||0)*-1)+\'px\')' : prop(s.top)) + ';' +
					       'left:' + (s.left == 'auto' ? 'expression(((parseInt(this.parentNode.currentStyle.borderLeftWidth)||0)*-1)+\'px\')' : prop(s.left)) + ';' +
					       'width:' + (s.width == 'auto' ? 'expression(this.parentNode.offsetWidth+\'px\')' : prop(s.width)) + ';' +
					       'height:' + (s.height == 'auto' ? 'expression(this.parentNode.offsetHeight+\'px\')' : prop(s.height)) + ';' +
					'"/>';
            return this.each(function () {
                if ($('> iframe.bgiframe', this).length == 0)
                    this.insertBefore(document.createElement(html), this.firstChild);
            });
        }
        return this;
    };

})(jQuery);